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SubjectRe: [PATCH v11 2/3]: perf record: enable asynchronous trace writing
On Mon, Oct 08, 2018 at 09:17:11AM +0300, Alexey Budankov wrote:

SNIP

> static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evlist,
> bool overwrite)
> {
> @@ -520,7 +644,10 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
> int i;
> int rc = 0;
> struct perf_mmap *maps;
> -
> +#ifdef HAVE_AIO_SUPPORT
> + int trace_fd = rec->data.file.fd;
> + off_t off;
> +#endif
> if (!evlist)
> return 0;
>
> @@ -531,14 +658,34 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
> if (overwrite && evlist->bkw_mmap_state != BKW_MMAP_DATA_PENDING)
> return 0;
>
> +#ifdef HAVE_AIO_SUPPORT
> + off = lseek(trace_fd, 0, SEEK_CUR);
> +#endif

I'm still little puzzled why we need to do this,
when the aio write takes the offset value, but
please provide some aio_.. function for this


> for (i = 0; i < evlist->nr_mmaps; i++) {
> struct perf_mmap *map = &maps[i];
>
> if (map->base) {
> - if (perf_mmap__push(map, rec, record__pushfn) != 0) {
> - rc = -1;
> - goto out;
> +#ifdef HAVE_AIO_SUPPORT
> + if (!rec->opts.nr_cblocks) {
> +#endif
> + if (perf_mmap__push(map, rec, record__pushfn) != 0) {
> + rc = -1;
> + goto out;
> + }
> +#ifdef HAVE_AIO_SUPPORT
> + } else {
> + /*
> + * Call record__aio_sync() to wait till map->data buffer
> + * becomes available after previous aio write request.
> + */
> + record__aio_sync(map);
> + if (perf_mmap__aio_push(map, rec, record__aio_pushfn, &off) != 0) {
> + lseek(trace_fd, off, SEEK_SET);
> + rc = -1;
> + goto out;
> + }
> }
> +#endif
> }
>
> if (map->auxtrace_mmap.base && !rec->opts.auxtrace_snapshot_mode &&
> @@ -547,7 +694,9 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
> goto out;
> }
> }
> -
> +#ifdef HAVE_AIO_SUPPORT
> + lseek(trace_fd, off, SEEK_SET);
> +#endif

ditto

thanks,
jirka

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